Characterization of a Dicer mRNA splice variant in oral cancer
Our research focuses on the study of RNA interference (RNAi) biology and how dysregulation of its molecular components can contribute to disease, in particular oral cancer. The goal of our research is to gain further insights into the molecular causes of oral cancer, identify novel biomarkers for this disease, and develop novel therapeutic strategies for treating oral cancer.
Dicer is a highly conserved RNase III type enzyme found in almost all eukaryotes that is essential for the RNA interference (RNAi) and microRNA pathways. During the last several years an increasing number of reports have found Dicer to be aberrantly expressed in different types of cancer, including oral squamous cell carcinomas (OSCCs). Recently, the dicer gene has been predicted to produce 11 mRNA splice variants bearing modified coding sequences. Our preliminary data suggests that one of these predicted Dicer mRNA splice variants is expressed in cells and appears to be upregulated in OSCC cell lines. Because the expression and function of the Dicer mRNA splice variants have not been well characterized and it currently remains unclear as to their biological significance, the focus of our research during the COBRE award period will be to explore the role of this particular Dicer mRNA splice variant in relation to oral cancer biology. Our overall hypothesis is that the dysregulation of the Dicer mRNA splice variant contributes significantly towards the progression and potentially the aggressiveness of oral cancer. Therefore, to better assess and correlate the expression patterns of the Dicer mRNA splice variant relative to OSCCs and disease progression we plan to (1) characterize its mRNA and protein expression levels in both OSCC cell lines and tissues ranging from dysplastic to invasive OSCCs in relation to non-cancerous counterparts. Furthermore, to enhance our understanding of the mechanisms regulating its aberrant expression we also plan to (2) analyze whether its aberrant expression in oral cancer cells is due to transcriptional and/or post-transcriptional regulatory mechanisms. Because the significance of the dysregulation of this splice variant in terms of cancer cell properties is not understood, we will also (3) examine the biological effects of reducing the levels of the Dicer mRNA splice variant in oral cancer cells using RNAi knockdown strategies and (4) analyze the effects of overexpressing it in both primary and immortalized human oral keratinocytes. The biological metrics will include cell proliferation, apoptosis, cell migration and invasion, and oncogenic transformation assays. By successfully addressing these specific aims this will lead to a better understanding of oral cancer biology. Furthermore, it will shed new insights into the function of Dicer mRNA splice variants and what roles they play in oral cancer progression.
Jakymiw A., R.S. Patel, N. Deming, I. Bhattacharyya, P. Shah, R.J. Lamont, C.M. Stewart, D.M. Cohen, and E.K.L. Chan. Overexpression of Dicer as a result of reduced let-7 microRNA levels contributes to increased cell proliferation of oral cancer cells. Genes, Chromosomes & Cancer. 49:549-559. (2010)